#11091 LOW Not Tri: XO-1.75 B1s have noticable bright spots in LED indicators

[Zarro Boogs per Child]

#11091: XO-1.75 B1s have noticable bright spots in LED indicators
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           Reporter:  greenfeld  |       Owner:  wad        
               Type:  defect     |      Status:  assigned   
           Priority:  low        |   Milestone:  Not Triaged
          Component:  hardware   |     Version:  1.75-B1    
         Resolution:             |    Keywords:             
        Next_action:  never set  |    Verified:  0          
Deployment_affected:             |   Blockedby:             
           Blocking:             |  
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Changes (by Quozl):

  * type:  enhancement => defect


Comment:

 Subjective assessment: the material of the light pipes in earlier
 production was:
  * opacity: very low
  * translucency: very high
  * transparency: very very low

 Most of the light was diffused.

 Subjective assessment: the material of the light pipes in current
 production is:
  * opacity: very low
  * translucency: high
  * transparency: low

 This increase in transparency results in some direct or reflected
 emission, with the remaining light diffused.

 A specification might include maximum or minimum values for opacity,
 translucency, and transparency.

 I've tested the new material briefly, with the front panel bezel taken out
 of a laptop.  I confirm the observations made by Sam.

 A bezel assembly test procedure might be something like:
  * construct a test rig that places the top edge of the bezel on a flat
 surface, with the bottom edge tiled up by 34mm (13 degrees), and place a
 light source underneath the battery LED light pipe,
  * inject light into the input side of the battery LED light pipe, using a
 vertically mounted white LED,
  * observe the output side of the pipe,
  * change the position of the light source back and forth by about 10mm,
  * fail the test if the light emitted is not uniform, as compared to a
 known good sample, and excluding the etched area,
  * gradually cover the input side with an opaque material, (such as a
 yellow sticky upside down) from one direction,
  * fail the test if the position of the opaque material can be determined
 on the output side.

 XO-1 B2 front bezel passes; there is some non-uniformity, but it is hard
 to detect.

 XO-1.75 B1 front bezel fails.

 The test is unfortunately somewhat subjective.  There would need to be a
 way to measure the brightness of the bright spots compared the brightness
 of the not-bright spots.

 A laptop test procedure might be something like:
  * insert battery, insert DC power plug, wait for green or orange battery
 LED,
  * observe the front of the light pipe, from a position perpendicular to
 the bezel,
  * angle the laptop by at least 35 degrees in each axis (up down, left
 right),
  * fail the test if bright spots from the LEDs are clearly identifiable.

 Also observed; the black foam between the light pipe entry points is
 shorter on the XO-1.75 B1 than it was on the XO-1 B2.  Not by much.  But
 the foam probably does not reach the PCB.  Vernier caliper weapon set to
 ''penetration'' says 3mm gap, with the power LED top surface 0.5mm above
 the PCB.

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Ticket URL: <http://dev.laptop.org/ticket/11091#comment:2>
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